1. Field of the Invention
The present invention relates to a semiconductor device in which transistors each having a gate insulating film with different thickness are formed on a substrate, and a manufacturing method thereof. In particular, the invention relates to a semiconductor device of which manufacturing steps can be simplified by doping impurities at a time, and a manufacturing method thereof.
2. Description of the Related Art
In manufacture of a CPU and a panel on the same substrate, when forming a thin film transistor of the CPU and a thin film transistor of the panel to have respective gate insulating films with different thickness, steps of doping impurities to a low concentration impurity region (LDD region) and steps of doping impurities to source and drain regions are separately performed on the CPU side and the panel side.
When performing impurity doping separately on the CPU side and the panel side as set forth above, steps are disadvantageously complicated. Thereupon, impurity doping is desirably carried out at a time in order to simplify the steps.
The invention is made in view of the aforementioned problem, and it is an object of the invention to provide a semiconductor device of which manufacturing steps can be simplified by doping impurities at a time, and a manufacturing method thereof.